Comparison of the Effects of Vibratory Foam Rolling and PNF Stretching on Calf Muscles Flexibility, Active joint position sense, and Dynamic Balance in Female Athletes with Chronic Ankle Instability in High-Impact Sports

The purpose of this study is to compare the immediate effect of vibrating foam rolling versus PNF stretching on calf muscle flexibility, ankle proprioception, and dynamic balance among female athletes in high-impact sports suffering from chronic ankle instability.

In this single-blind, randomized crossover trial (n=23), participants recruited via purposive sampling from Shiraz sports clubs will receive both interventions in a randomized sequence. A 48-hour wash-out period will be implemented to prevent carry-over effects, with randomization performed via 'Randomizer' software.

This randomized crossover trial, conducted at the Shiraz University of Medical Sciences' Rehabilitation Clinic, compares the immediate effects of vibrating foam rolling and PNF stretching on the calf muscles. Both interventions consist of three 60-second sets with 30-second rest intervals. To eliminate bias, variables are measured pre- and post-intervention by a blinded assessor unaware of the sequence.

Female athletes (≥18 years) playing contact sports (e.g., volleyball, basketball, futsal, kickboxing) 3 times/week were recruited. Inclusion criteria: at least one unilateral ankle sprain in the past year with associated pain/swelling, self-reported instability, and a CAIT score 25. Exclusion criteria: joint hypermobility, neurovascular or musculoskeletal lower-limb disorders (except ankle sprains), head injury or low back pain (last 6 months), ankle fractures, grade 3 sprains requiring surgery, lower limb surgery (last 12 months), bony restrictions, vestibular/balance disorders, and neuropathies.

Two types of warm-up techniques before exercise: vibrating foam rolling and PNF stretching.

Calf Muscles Flexibility, Active joint position sense, and Dynamic Balance

Randomization and Allocation: Participants were randomly assigned to either the vibrating foam rolling group or the PNF stretching group. A computer-generated random sequence was produced using the "Randomizer" software. The unit of randomization was the individual participant, and no stratification was applied. Allocation concealment was ensured by keeping the group assignment hidden until the point of intervention. Blinding: To minimize bias, an assessor-blinded design was implemented. The researcher responsible for performing the functional and balance tests was blinded to the group allocation and the specific intervention received by each participant.

A single-blind design (assessor-blinding method) was employed in this study. To implement this process, the interventions (vibrating foam rolling and PNF stretching) were administered by another individual, and the assessor (the researcher) was not present during the intervention sessions. Pre- and post-test evaluations were conducted by an assessor who was unaware of the specific intervention received by the participants. Furthermore, to prevent the disclosure of group